Principles of Genetic Inheritance Flashcards
Genomic imprinting
Certain genes are expressed only from the mother or father. Imprinted alleles are silenced such that the gene is only expressed from the non-imprinted allele of the mother or father
This is an epigenetic process
-Can lead to Prader-Willis syndrome
Uniparental disomy
When an individual receives two copies of a chromosome or part of a chromosome from one parent and none from the other parent
Related to non-disjunction
-Can lead to Prader-Willi syndrome
Robertsonian vs Reciprocal translocation
Robertsonian- long arm of two acrocentric chromosomes are combined, short arms typically lost
Reciprocal- Exchange of material b/w nonhomologous chromosomes
Turner syndrome
45, XO
Female, no Y chromosome
Ovarian hypofunction
Most do not undergo puberty and are infertile
Cardiovascular defects, no cognitive defects
Prader-Willis syndrome/Angelman syndrome
Deletion of a region of chromosome 15
Phenotype depends on which parents chromosome was deleted
Paternal-short stature, hypotonia, small hands/feet, obese, mild intellectual disability
Maternal=Angelman syndrome- severe intellectual disability, seizures, ataxic gait
Klinefelter syndrome
47, XXY (could also be 48 XXXY or 49 XXXXY-worse symptoms)
Varying cognitive, social, behavioral difficulties
Small, undescended testes
Tall stature, infertility
Trisomy 21
47, XX +21
Results most commonly from maternal meiotic non-disjunction
Trisomy 18 Edwards syndrome
47, XX +18
Most die in utero
Trisomy 13 Patau syndrome
47, XX +13
Most die before birth
Penetrance
The frequency in which a gene manifests itself
If phenotype occurs in 90% of people who inherit gene defect, there is 90% penetrance
Locus heterogeneity
Single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci
Only one mutant locus is needed for the phenotype to manifest
Multifactorial inheritance
Recurrence risk is higher if the proband is of the less commonly affected sex
